This invention relates to a switching device, and more particularly to an arc self-extinguishing switch device for self-extinguishing an electric arc established across a pair of contact members through the utilization of a gas expanded with heat generated by the electric arc.
There have been recently developed simple, highly economical switch devices of the above type including an amount of an arc extinguishing fluid such as gaseous sulfur hexafluoride (SF.sub.6) filling an arc extinguishing compartment having a suitable volume and operative to place the are extinguishing fluid under a high pressure through the utilization of the pressure increasing action resulting from thermal energy mainly provided by the electric arc itself and to extinguish the electric arc by delivering the fluid forming a high pressure source to an arc space in the process of decreasing the resulting arc current to a null magnitude.
In conventional switching devices of the type referred to, it is indispensable to increase the pressure of the arc extinguishing fluid within the pressure increasing compartments at a temperature as low as possible. This is because the pressure of the arc extinguishing fluid rises with thermal energy resulting from the particular electric arc itself. When the electric arc enters into the pressure increasing compartment, the pressure of the arc extinguishing fluid is apt to rise, but a disadvantage has been caused in that the temperature of the arc extinguishing fluid is prone to rise, thus resulting in that the arc extinguishing performance is reduced.
Accordingly, it is an object of the present invention to provide a new and improved switching device operative to maintain an amount of an arc extinguishing fluid at a temperature as low as possible, which fluid charges a pressure increasing compartment and increases in pressure upon the occurrence of an electric arc while being highly capable of performing the arc interrupting or extinguishing operation.